Add 'Downloads' page aliases

On the old site, '<home>/download' would render the '<home>/downloads' page,
so add a symlink from 'download/index.html' to 'downloads/index.html'.

Additionally, add explicit OS aliases for the '<home>/download/gui/<os>'
pages to allow direct OS filter links to work. The 'application.js' OS
filtering functionality handles filtering the page content based on the URL
already, so there's no noticeable change to the functionality.

Note that, because we cannot do custom routing,
'<home>/download/gui/<invalid value>' will no longer render the unfiltered
GUI page, instead routing the user to a 404.

Signed-off-by: Victoria Dye <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: vdye

content/download/_index.html

@@ -0,0 +1,3 @@
+---
+redirect_to: downloads
+---

content/download/gui/_index.html

@@ -0,0 +1,3 @@
+---
+redirect_to: downloads/guis
+---

content/downloads/guis/android.html

@@ -0,0 +1,5 @@
+---
+redirect_to: downloads/guis?os=android
+aliases:
+- /download/gui/android
+---

content/downloads/guis/ios.html

@@ -0,0 +1,7 @@
+---
+redirect_to: downloads/guis?os=ios
+aliases:
+- /download/gui/ios
+---
+
+

content/downloads/guis/linux.html

@@ -0,0 +1,6 @@
+---
+redirect_to: downloads/guis?os=linux
+aliases:
+- /download/gui/linux
+---
+

content/downloads/guis/mac.html

@@ -0,0 +1,7 @@
+---
+redirect_to: downloads/guis?os=mac
+aliases:
+- /download/gui/mac
+---
+
+

content/downloads/guis/windows.html

@@ -0,0 +1,7 @@
+---
+redirect_to: downloads/guis?os=windows
+aliases:
+- /download/gui/windows
+---
+
+